PCIe x4 to PCI 32 bit bridge

PCIe to PCI 32bit forward bridge, transparent mode.

The bridge connects to the host side using a PCIe Gen1 x4 link, providing full bandwidth for 32bit PCI@66MHz. It is designed to be installed next to the motherboard, using standoffs and a PCIe extender cable.

Specs:
-x4 PCIe Gen1 link, providing full bandwidth for 32bit PCI@66MHz (and more)
-32 bit PCI slot, 5V keyed, accepting either 5V or universal cards. 3.3V only PCI cards can be installed if the notch is removed.
-on board power -12V, 5V and 3.3V power supplies, with maximum current exceeding PCI specs. All power is drawn from the PCIe power connector.
-configurable PCI clock, using the tactile switches on the board, in 1MHz increments, from 25MHz up to 133MHz.
-additional PCI clock values can be configured using the on board USB connector, for example 78.545MHz.
-peristent PCI clock setting
-if the clock is changed during operation, it is applied at the next power off/power on cycle or when the system is rebooted.

The bridge can also be configured as a basic one:
-non-programmable clock, automatic 33/66MHz or 25/50MHz selection, no display, USB connector, tactile switches. Jumper option for forcing 66MHz operation on 33MHz PCI cards.

It was successfully tested on various modern systems, mostly with 3dfx cards, V2, V3 2000, Vodoo Banshee, Voodoo Rush, V4 4500, V5 5500, with good results. However, depending on the motherboard/BIOS, there may be incompatibilities.

Full design files (schematic, PCB, gerbers, BOM) and source code will be uploaded at a later date.

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